Moisture absorbent material and articles incorporating such material

ABSTRACT

A moisture absorbent material comprises a porous matrix of absorbent alumina, the volume of the pores of the matrix being between 60 and 90%, preferably 80 to 85% of the volume of the material. The average diameter of the pores is between 5×10 -9  and 1×10 -6  m. The pores contain a crystalline deliquescent compound, preferably calcium chloride, in an amount of between 4 and 20%, preferably between 8 and 12%, by weight, excluding any water of crystallization, with respect to the total weight of the material. The absorbent may be incorporated in a shoe insole and absorbs up to 1.5 ml moisture per gram of dry material whilst generating heat, thereby maintaining the feet of the user both warm and dry.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a moisture absorbent material and articlesincorporating the material, particularly articles of clothing andfootwear and components thereof.

2. Description of the Prior Art

The absorption of moisture from the environment or the reduction ofmoisture or humidity in a restricted space is desirable in variousfields, for example in containers or the like. To this end a widevariety of moisture absorbent materials has been developed over theyears.

SU-A-1452566 discloses a water absorbent material consisting of a porousgranular material formed by moulding and heat treating a plastichomogenized paste containing active aluminium oxide in the form of 40 μmparticles (30-55% by weight), clay (3-22% by weight), active carbon(4-10% by weight) and lithium bromide (36-45% by weight). This materialis used to dry currents of air and other gases, its principal use beingin breathing apparatus filters for protection against carbon monoxide.However, it is unsuitable for direct contact with human skin because itcontains toxic lithium bromide, and in any case its moisture absorbencyis inadequate for many purposes since it absorbs moisture at a maximumrate of 20 g per hour and per liter of this material. Moreover itsmoisture absorbency at a temperature of 27°-33° C. and 80% humidity is amere 0.2 g/ml of this material. The reason for the inadequate waterabsorbency is thought to be that the components of the material arepresent in dense fine particulate form which means that only thesurfaces of the particles are active, that is to say absorb and adsorbmoisture.

SU-A-406552 discloses a moisture absorbent material which containsactive carbon in granular form with a grain size of 1.00-2.75 mm, whichis saturated with a mixture of lithium chloride and calcium chloride.The constituents are present in the following proportions by weight:active carbon (68-72%), calcium chloride (18-20%), lithium chloride(10-12%).

This material is used successfully in breathing apparatus for protectionagainst carbon monoxide. However, the high content of deliquescentsubstances (LiCl and CaCl₂) means that a salt solution is formed by theadsorption of water which tends to escape from the pores of the activecarbon matrix under high humidity conditions. In any event the toxicityof lithium chloride precludes direct contact with human skin. Moreoverthe low mechanical strength of active carbon results in the destructionof the material when under stress.

SU-A-1729427 discloses a shoe insole which includes a component made ofhydrophobic material with depressions on its upper surface in whichhydrophilic material is received and wrapped in perforated hydrophobicmaterial. The lower layer of this component is made of metallized foilto reflect radiated energy back into the foot.

However, this proposal has several significant drawbacks. Theinefficient use of the entire surface of the insole (effectivecoefficient 0.5) makes it impossible to achieve the requiredmoisture-absorbent rate; whatever material is used for the insoles, itadsorbs only moisture in the form of vapor when in motion, and, thenon-uniform moisture absorption through the perforations in thehydrophobic wrapper causes a significant reduction in themoisture-absorbent capacity of the insole, since heat is not transferredlengthwise (the depressions are separated by a hydrophobic medium).Moreover the regeneration of the moisture absorbent properties, afteruse, is complex. The heat protection and moisture absorbent propertiesof the insole cannot be fully restored.

The advantages of using moisture-absorbent materials in the clothingfield is well known, particularly in the field of footwear. All thephysiological functions of the human body are interdependent. As ahomoisothermal system the body strives to maintain its temperature at aconstant level of 37°±0.8° C.

Many researchers consider that the temperature of the foot should bebetween 27° and 33° C. at a relative humidity within the shoe of 50-70%.These levels are also regarded as the main criteria determining comfort.If the parameters fall outside these ranges the result is discomfort.

The main problem which makes it difficult to achieve optimum heatmanagement of the feet, for example, is perspiration--amounting onaverage to 1 g per hour at rest and up to 15 g per hour during intensephysical effort. This results in a high humidity equilibrium in theenclosed space within the shoe, normally about 100% relative.

When clothing or shoes are worn, a transfer of both moisture and heatcan be observed in the body/shoe--clothing/shoe--environment system. Theaccumulation of moisture in the material of clothing or shoes has amarked effect during wear on the limits of comfort. While a certaincombination of shoe materials (knitted fabric+lining+outer lining+upper)creates comfortable conditions for the foot (27° C.) in an ambienttemperature of -9° to +20° C. at 40% humidity, in dry conditions thesame materials produce comfort at ambient temperatures of -20° to +14°C. At lower temperatures the feet feel cold, while at highertemperatures they feel hot. If excess sweat and moisture are not removedvia clothing or the materials of which the shoe is made, the moisturecondenses as the ambient temperature falls. This substantially increasesthe heat conductivity of the clothing material, the sole and the otherfootwear components, and therefore the heat loss from the body or foot,thereby cooling it excessively. At maximum moisture content the heatconductivity of commonly-used footwear materials increases by a factorof between 5 and 7, approaching that of water (0.55 W/m*K).

It is also known that various microbes, yeasts and fungi are found onthe skin of the foot. The temperature and high humidity in the shoe, incombination with the salts and fats contained in sweat, constitute anideal breeding ground for the development of mycosis and fungalinfections--from which roughly half the population suffers. Similarconditions prevail in the armpit region.

The creation of optimum temperature and humidity conditions provides thesolution, increasing the sense of well-being, improving resistance tocoryza and fungal infections and increasing the working capacity of theuser.

Moisture absorbent materials such as untreated cotton, active carbon andmetallic salts are used in the manufacture of insoles (see, for example,DD-A-273679 or DE-A-3938825) with the idea of improving heat managementin the foot within the shoe throughout the entire period for which it isworn. However, the moisture absorbency of these materials is notsufficient to ensure optimum conditions for the foot for such aprotracted period.

The object of the present invention is to avoid the disadvantages ofprevious moisture absorbent materials while providing an improvedmoisture adsorption capacity and preferably also a simultaneous exchangeof both moisture and heat.

The further object of this invention is to improve the wearing qualityand comfort of clothing, particularly footwear such as winter and sportsfootwear.

SUMMARY OF THE INVENTION

According to the present invention a moisture absorbent materialcomprises a porous matrix of adsorbent material, the volume of the poresof the matrix being between 60 and 90%, preferably between 80 and 85% ofthe volume of the material and the average diameter of the pores beingbetween 5×10⁻⁹ and 1×10⁻⁶ m, the pores containing a crystallinedeliquescent compound in an amount of between 4 and 20%, preferablybetween 8 and 12% by weight, excluding any water of crystallization,with respect to the total weight of the material.

The material of the present invention thus absorbs and retains moistureby a combination of adsorption by the matrix material and absorption bythe deliquescent material which in practice will probably firstly absorbwater in the form of water of crystallization and will then turn into asolution and continue to absorb water by the phenomenon ofdeliquescence. As it does so heat is also generated by the material andthus warms the body of the user of the material which is incorporated ine.g. an article of clothing or a shoe insole. Due to the substantialoverall pore volume of 60 to 90%, e.g. 85% of the total volume of thematerial, and the small pore size, the available surface area of thematrix material is very substantial indeed, i.e. 50 to 250 m² /g. Thismeans firstly that the matrix material can adsorb a relatively largevolume of moisture. More importantly, the deliquescent compound isdistributed in the form of small crystals throughout the matrix materialand thus also presents a large surface area at which moisture isabsorbed. When the crystals turn into a solution there is of course thetendency of the solution to run out of the pores of the material butthis tendency is resisted by the adsorptivity of the matrix and by thesurface tension effect exerted by the very large number of very smallpores. Thus the present invention allows the full potential of theadsorptivity of the matrix and the absorptivity of the deliquescentmaterial to be made use of in combination without the disadvantage of afresh solution of deliquescent salt being produced and then running outof the material.

The principal novel characteristic of the material in accordance withthe invention derives from the fact that it combines the traditionalmechanisms of moisture adsorption through the surface of the materialand moisture absorption by a deliquescent salt solution. This makes itpossible to "design" a moisture absorbent material precisely appropriateto the task in hand.

Moisture absorption by the material releases the heat of condensationand adsorption and this amounts to typically 1-1.5 W per 1 g/hour ofmoisture absorbed.

The temperature at which adsorbed water is displaced, i.e. theregeneration temperature, is typically quite high, e.g. in excess of100° C. However, it is found that this temperature is substantiallyreduced if the adsorbent material is in fine pored form and a largenumber of small crystals of a deliquescent compound are distributed inthe pores. The temperature at which the water adsorbed by a deliquescentcompound is driven off is in any event typically relatively low. Thismeans that the regeneration of the material in accordance with theinvention takes place under moderate temperature conditions, preferablyat temperatures of less than 60° C., e.g. between 35° and 45° C., whichmeans that it can be used in clothing, e.g. as lining or padding,optionally only in limited regions such as the back and armpits, or forfootwear, particularly for insoles, lining material or inner shoes butnevertheless easily regenerated by a domestic user. The term "insole" isused herein to describe any shoe sole other than the outer sole, i.e. atraditional insole or inner sole or a so-called midsole. Owing to itsmoisture absorbent and temperature-regulating effect the material inaccordance with the invention can also be used with advantage in themanufacture of permanent or removable seat covers, covers forupholstered furniture and for seats in cars or other vehicles.

Whilst the material may be provided in a number of forms, e.g. plates orsheets, it is preferred that it is in granular form, preferablysubstantially spheroidal form with a diameter of between 0.01 and 3 mm,more preferably between 0.1 and 2 mm. The matrix may comprise a numberof suitable adsorbent materials, such as aluminosilicate material, butit is preferred that it is active aluminium oxide. This substance hasthe mechanical strength necessary for footwear or clothing subject toheavy wear and is also non-toxic, i.e. compatible with the human skin.

As mentioned above, the overall pore volume of the material is between60 and 90%, preferably 80 to 85% of the volume of the material. Its bulkdensity is preferably 0.2 to 0.6 g/cm³ (ideally 0.3 to 0.4 g/cm³). Thespecific surface area is preferably more than 150 m² /g (ideally morethan 200 m² /g).

It has been found that the quantity of absorbed moisture (before thesolution flows out of the pores) depends on the ambient humidity and onthe quantity of the deliquescent compound within the pores, and that itis greater than the sum of the moisture adsorbed by the pure matrix plusthe moisture absorbed by the equivalent amount of the deliquescentcompound. The reason for this is that the deliquescent compound ispresent in very finely divided form, i.e. it has a very large surfacearea.

If a correctly "designed" material is incorporated into a shoe insole itwill absorb up to 0.45 milliliters of moisture per gram of the material.This value exceeds the level of all previously known absorbents by afactor of at least 2 or 3. The rate at which the process takes place issubstantially reduced when all the pores are full of moisture, becauseat this point moisture adsorption by the matrix surface ceases and thesurface of the moisture absorbing solution is substantially smaller.Moisture absorption by the material can thus be said to switch itselfoff. The time when this happens depends on the relative humidity atwhich the material is functioning and on the quantity of deliquescentcompound in the matrix pores. When used in shoes, on the basis that thehumidity within the shoe is always above 80%, this results in an optimumquantity of deliquescent compound in the matrix pores of 8-12% byweight.

The solution formed by the deliquescent compound is prevented fromrunning out of the material by the meniscus or surface tension effect ofthe small pores. The solution therefore does not run out provided thatthe retaining effect of surface tension is greater than the expansioneffect on the solution within the pores caused by the attraction of thesolution to water produced by the deliquescent compound. The retainingor surface tension effect increases with decreasing pore size whilst thetendency of the solution to run out of the pores increases withincreasing concentration of the solution, i.e. with increasing contentof the deliquescent compound. These two factors must be balanced butwith the pores of the size referred to above a content of thedeliquescent compound of 8 to 12% by weight is sufficiently low toensure that the solution does not run out of the pores. If the contentof the deliquescent compound is significantly below this level the rateof moisture absorption and heat evolution will drop to potentiallyunacceptable levels.

Whilst a number of deliquescent compounds may be suitable, it ispreferred that calcium chloride be used.

This is non-toxic and absorbs 6 molecules of water of crystallizationper molecule and then deliquesces. Calcium chloride is easilyregenerated at low temperature, and thus when exposed to a temperatureof 40° to 60° C., e.g. on a domestic radiator or boiler, the solutionfirstly crystallizes and then the number of molecules of water ofcrystallization reduces to 2. A temperature in excess of 100° C. isrequired to remove the last two molecules of water and whilst this canbe achieved in the home, e.g. in a microwave oven, it is not necessaryto do so and the total absorbency of the material is scarcely reducedthereby. When calcium chloride is present in an amount of 8 to 12% byweight, measured in the anhydrous form, the material will absorb 30 to200 g/hour per liter of material and releases heat whilst doing so.

The matrix may include a substance, such as active carbon, to remove theodor which can be created by the bacteria which typically live in shoes.Similarly, the matrix may include a perfume or the like or a bactericideor a fungicide. Such materials may be incorporated in the matrixmaterial during its manufacture, which will be described below, in solidform.

The invention also embraces a moisture absorbent article incorporatingmaterial of the type described above. The article may constitute anarticle of clothing or a part or component of an article of clothing ora component of a shoe, in particularly an insole. The moisture absorbentmaterial may in practice be situated beneath or within a moisturepermeable cover sheet or be sandwiched between two such sheets. Thearticle may be in direct contact with the skin of the user, whichoptimises the moisture absorbent effect and the benefit of the heatgeneration.

An insole may comprise two or three interconnected layers of material,of which one or the two outer layers are moisture permeable material andthe middle layer defines at least one space filled with the moistureabsorbent material. The middle layer may consist of unwoven fibrousmaterial in which the moisture absorbent material is distributed ingranular form. Alternatively, the middle layer may afford perforatedstiffening ribs, e.g. extending in one or more sets of parallel ribs,between which there are communicating spaces filled with the moistureabsorbent material.

Further features of the invention will be apparent from the followingdescription of one specific embodiment of making a moisture absorbentmaterial in accordance with the invention and of a number of shoeinsoles incorporating such a material.

Substantially spheroidal granules of moisture absorbent material may bemade by making an aqueous solution of sodium aluminate (NaAlO₂) and thenprecipitating aluminium hydroxide in solid form, so-calledpseudoboemite, by adding an acid or aluminium salt. The precipitate iswashed and mixed into a creamy consistency and dropped through a tube orthe like into the upper portion of a reaction vessel which containskerosene or light oil in its upper portion floating on a solution ofammonia or water rendered ammoniacal by bubbling ammonia gas through it.The suspension is immiscible with the kerosene and breaks up intospherical globules whose diameter is determined principally by theconcentration of the solution but is typically set to be between 0.1 and2 mm. These globules sink through the kerosene due to their greaterdensity and then enter the ammoniacal solution and where they harden toform solid porous granules of aluminium hydroxide.

The aluminium hydroxide granules are then removed from the reactionvessel and dried and heated in three stages, firstly for a few hours inair, secondly for 10 to 12 hours at a temperature of 110° to 140° C. andthirdly for 5 to 6 hours at a temperature of 550° C. At this elevatedtemperature the aluminium hydroxide decomposes to form alumina andwater. The total pore volume of the resulting alumina granules and thepore sizes may be adjusted by varying the process parameters and are setto be within the ranges set forth above. This method of making porousalumina granules is known per se and is disclosed in a monograph byAlvin B Stiles, published by Butterworth Publishers in 1987 and entitled"Catalyst Supports and Supported Catalysts", M. Chemistry 1991. Thegranules are, however, only known for use as catalyst supports.

An inorganic deliquescent compound, in this case calcium chloride, isthen introduced into the pores of the granules. This may be effected bytwo different methods. In the first method a weighed amount of granulesis placed in a vessel and continuously agitated. An amount of calciumchloride which will constitute between 8 to 12% of the finishedgranules, measured on an anhydrous basis, is then dissolved in a limitedamount of water which is sprayed onto the granules. Due to the agitationof the granules the calcium chloride solution is distributed uniformlyover all the granules and absorbed by them into their pores. In thesecond method, the alumina granules are immersed in a relatively dilutesolution of calcium chloride and fully saturated. The concentration ofthe solution is such that the mass of CaCl₂ taken up by the granuleswill constitute 8 to 12% by weight, on an anhydrous basis, of thefinished granules. In both cases the granules are then dried and thecalcium chloride is left within the pores of the granules, finelydistributed in crystalline form. Each molecule of CaCl₂ will then have 2molecules of water of crystallisation unless the drying is performed ata sufficiently elevated temperature to drive them off, in which case theCaCl₂ will be fully anhydrous, though this is not necessary. Themoisture absorbent granules are then ready for use.

BRIEF DESCRIPTION OF THE DRAWINGS

Two embodiments of shoe insole incorporating granules in accordance withthe invention will now be described with reference to the accompanyingdrawings, in which:

FIG. 1 is a plan view, partly cut away, of the first embodiment;

FIG. 2 is a longitudinal sectional view on the line A--A in FIG. 1;

FIG. 3 is a view similar to FIG. 1 of the second embodiment; and

FIG. 4 is a view, similar to FIG. 2, but is taken on the line B--B inFIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The insole shown in FIGS. 1 and 2 includes an upper layer 1 and lowerlayer 2 which are manufactured from hydrophilic, moisture permeableelastic fabrics in the shape of a foot profile and between which is amiddle layer 3. The upper layer 1 has a thin, soft surface and itspurpose is to provide a comfortable surface for the sole of the foot.This layer allows water vapor to pass through to the granular materialin the middle layer and provides high heat conductivity from the middlelayer to the foot. The lower layer 2 consists of a coarse fabric with avapour permeability coefficient of at least 20 mg/cm per hour at a vaporpressure differential of 2,300 Pa. The layer 3 includes a beaded edge 4with a right-angled profile which consists of non-woven foam or solidmaterial, the purpose of which is to provide the correct thickness ofthe insole, to connect the edges of the layers 1 and 3 and to stabilisethe insole under intensive dynamic stress. In the heel part of theinsole the beaded edge is enlarged at 5 to produce a shock-absorbingarea for the foot when walking.

The middle layer 3 of the insole consists of space-filling unwovenfibrous material with e.g. a maximum of 50 ml of the granular material 6evenly distributed among the fibres. The quantity of the material isdetermined by the type and size of insole and by the desired rate andvolume of moisture absorption. The granules are in vapor communicationwith each other and with the entire surface of the upper layer 1, thuspermitting the moisture from the foot, in both vapor and liquid form, tobe transported vertically as well as longitudinally and transversely.This is an important property, since the foot gives off perspirationmainly in the region of the toes. An even distribution of moisture overthe whole volume of the inset sole ensures that the heat, which isgenerated by the granules as they absorb moisture, is also evenlydistributed over the whole surface in contact with the foot.

The layers 1, 2 and 3 are connected to each other by sewing with aheavy-duty sewing machine with a distance of 10-15 mm between stitches8. The choice of fabric for the upper and lower layer, the thickness ofthe fibrous material and the quantity of the granules provide therequired thickness of the insole and the period of effective moistureabsorption and heat release under varying physical stress and ambientconditions.

The insole shown in FIGS. 3 and 4 includes a similar upper layer 1 andlower layer 2. The middle layer 3 is manufactured by casting or punchingelastic foam of the required thickness and reproduces the "anatomical"profile of the foot. Its entire volume is bounded by an enclosed edgeand it has interior walls 9 with apertures 4 creating interconnectedhollow spaces 10. In the toe and heel area of layer 2 are enlargementswhich produce a shock-absorbing function for the foot when walking.

The middle layer 3 is bonded to the lower layer 2 by adhesive with thespaces 10 filled with the appropriate quantity of moisture absorbentmaterial and sewn to the upper layer 1 using a heavy-duty sewingmachine.

The moisture absorbent material is capable of absorbing up to 1.5milliliters of moisture per gramme of material at a temperature of27°-30° C. and humidity of 80% without changing its physical state, i.e.with no calcium chloride solution escaping from the matrix pores. Inuse, the calcium chloride will absorb water of crystallization untilthere are 6 molecules of water of crystallization per molecule ofcalcium chloride. It is solid in this state when at a temperature ofless than 27° C. but when in a shoe it will usually be at a temperatureof more than 27° C. and it thus liquefies. The large area of thesolution means that it continues to absorb water due to itsdeliquescence until the pores are full and the rate of absorption thensubstantially reduces. However, the solution is retained within thepores of the granules and can not run out.

It has been established that at a calcium chloride content of less than8% by weight the desired rate of moisture absorption is not achieved,while at a calcium chloride content of more than 12% by weight the saltsolution may escape from the pores of the aluminium oxide matrix whenthe temperature and humidity within the shoe are at the levels referredto above.

It has been established that when moisture is absorbed the release ofheat within the shoe (adsorption heat and condensation heat) totals1.0-1.5 W per 1 g/hour of absorbed moisture.

The regeneration of the saturated material takes place under moderatetemperature conditions of between 35° and 60° C. and can thus beeffected on e.g. a domestic radiator.

EXAMPLE 1

Moisture absorbent material in granular form with a grain size up to 2.0mm. This material is a calcium chloride saturated granular aluminiumoxide with a specific surface area of 200 m² /g and a pore volume of0.65 cm³ /g. At a temperature of 30° C. and 80% humidity 50 ml of thismaterial, which contains 4 g of calcium chloride, absorb between 20 and23 grams of moisture. No escape of the calcium chloride from the matrixpores is observed.

EXAMPLE 2

Moisture absorbent material in granular form with a grain size of 0.5mm. This material is a calcium chloride saturated granular aluminiumoxide containing minute particles of active carbon in the pores. At atemperature of 30° C. and 80% humidity 50 ml of this material, whichcontains 5 grams of calcium chloride and 0.25 g of active carbon, absorbbetween 20 and 23.5 grams of moisture. No escape of the calcium chloridefrom the matrix pores is observed.

EXAMPLE 3

A pair of insoles was manufactured according to the first embodimentwith the inclusion of 50 ml of granular material. Every day for 30 daysthey spent 8 hours inside winter shoes at an ambient temperature of20°-23° C. and 2 hours at a temperature of -15° to -20° C. Theregeneration of the insoles took 10 hours at a temperature of 40°-60° C.The insoles were weighed each day before being worn. The daily quantityof moisture absorbed and the quantity of heat given off by the insolesremained unchanged through the entire period.

The insoles actively absorb the moisture of the foot over an extendedperiod, thus creating comfortable temperature and humidity conditionsand keeping both the foot and the shoe dry. The essential heatinsulation properties of the shoe are preserved. The insole retains thecapacity to recover its properties in many successive wear-regenerationcycles.

Naturally many variations are possible within the scope of theinvention. The or each covering layer may be smooth or structured, haveprojections or no projections and be stiff or flexible. Possiblematerials include, for example, felt, textiles, rubber, polyurethane,synthetic resin, air-permeable non-woven fabric, woven fabric, knittedfabric, natural or synthetic fibres (viscose) or mixtures thereof,perforated or (only on one side) continuous metallic foils (e.g.aluminium), foam rubber, leather, synthetic leather and the like.

The various covering and intermediate layers can be connected by anysuitable method, for example by sewing, adhesive and the like, and thelayers can be connected within the edges by stepping, needling and thelike.

Finally the use of covering and intermediate layers can be avoided bytreating the moisture absorbent material with suitable binding agents toproduce soft or hard (or age-hardening) substances. This can itself beused to manufacture the above-mentioned clothing and footwear componentsand the like to achieve both the required mechanical strength and theshape of the article in question. A shaped insole or midsole could thenbe manufactured by moulding this substance and, if necessary, hardeningit. It may be appropriate to apply it to a carrier layer.

While preferred embodiments of the invention have been shown anddescribed in detail, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the basic principles of the invention as embraced by the followingclaims.

We claim:
 1. A moisture absorbent material comprising a porous matrix ofadsorbent active aluminium oxide, the volume of the pores of the matrixbeing between 80 to 85% of the volume of the material, the bulk densityof the matrix being between 0.3 and 0.4 g/cm³, the specific surface areaof the matrix being greater than 150 m² /g, and the average diameter ofthe pores being between 5×10⁻⁹ and 1×10⁻⁶ m, the pores containing acrystalline calcium chloride in an amount of between 8 and 12% byweight, excluding any water of crystallization, with respect to thetotal weight of the material, whereby the material may be substantiallyregenerated at a temperature between 35° and 45° C.
 2. The material ofclaim 1 wherein said material is in granular form with a diameter ofbetween 0.01 and 3.0 mm.
 3. The material of claim 2 wherein saidgranular form is substantially spheroidal.
 4. The material of claim 1wherein said material is in granular form with a diameter of between 0.1and 2.0 mm.
 5. The material of claim 4 wherein said granular form issubstantially spheroidal.
 6. The material of claim 1 wherein the matrixincludes a deodorizing substance.
 7. The material of claim 6 wherein thedeodorizing substance is active carbon.
 8. The material of claim 1wherein the matrix includes one or more of a perfume, a bactericide anda fungicide.
 9. An article incorporating moisture absorbent material,said material comprising a porous matrix of adsorbent active aluminumoxide, the volume of the pores of the matrix being between 80 to 85% ofthe volume of the material, the bulk density of the matrix being between0.3 and 0.4 g/cm³, the specific surface area of the matrix being greaterthan 150 m² /g, and the average diameter of the pores being between5×10⁻⁹ and 1×10⁻⁶ m, the pores containing a crystalline calcium chloridein an amount of between 8 and 12% by weight, excluding any water ofcrystallization, with respect to the total weight of the material,whereby the material may be substantially regenerated at a temperaturebetween 35° and 45° C.
 10. The article of claim 9 wherein said materialis in granular form with a diameter of between 0.01 and 3.0 mm.
 11. Thearticle of claim 10 wherein said granular form is substantiallyspheroidal.
 12. The article of claim 9 wherein the matrix includes adeodorizing substance.
 13. The article of claim 9 wherein the matrixincludes one or more of a perfume, a bactericide and a fungicide. 14.The article of claim 9 wherein said article is a shoe insole.
 15. Thearticle of claim 14 wherein said insole comprises at least twointerconnected layers of material, and wherein one of said layers ismoisture permeable and another of said layers defines at least one spacefilled with said moisture absorbent material.
 16. The article of claim15 wherein said layers of material comprise two layers of moisturepermeable material between which is a middle layer of unwoven fibrousmaterial, said moisture absorbent material being distributed in saidmiddle layer in granular form.
 17. The article of claim 16 wherein saidmiddle layer has a plurality of spaced apart perforated stiffening ribs,the spaces between said ribs being filled with said moisture absorbentmaterial.
 18. The article of claim 17 wherein said stiffening ribsextend in one or more sets of parallel ribs.